1. FIELD OF THE INVENTION
Portable electrical apparatus, including batteries for energizing the same, are used in many applications. These batteries may be rechargeable batteries, such as nickel cadmium batteries, so that they can be recharged rather than be replaced, and thereby a substantial cost saving is achieved. Some users of battery energized equipment may have need for batteries having substantially different capacities, and to properly charge batteries different charging rates should be used. A substantial cost and space saving is realized by providing a universal charging apparatus for charging the different batteries which require different charging rates. However, to accomplish this, it is necessary to provide control of the charging rate and to further provide timed and rapid charge functions. To provide this control, it is necessary to have information as to the required charging rate for the different batteries so that the proper charging rate can be set in the charging apparatus. It is desirable that the charging rate be automatically set for the battery which is to be charged, to prevent incorrect charging and minimize human error.
2. DESCRIPTION OF THE PRIOR ART
Prior art charging apparatus do not have the ability to sense the different required charging rates for batteries having different capacities and supply predetermined charging currents closely approximating the various required charging rates to the batteries. U.S. Pat. No. 3,767,995, entitled "Automatic Battery Charging Circuit Operable Over a Wide Temperature Range" for example, discloses apparatus for charging a battery at a first rate if there is no thermistor associated with the battery and at a second rate if a thermistor is present. However, there is no circuitry for automatically altering these charging rates for charging batteries with different capacities.